The data on sex were derived from answers to Question 1. Individuals were asked to mark either "male" or "female" to indicate their sex. For most cases in which sex was not reported, the appropriate entry was determined from the person's given (i.e., first) name and household relationship. Otherwise, sex was imputed according to the relationship to the householder and the age of the person.

The sex ratio represents the balance between the male and female populations. Ratios above 100 indicate a larger male population, and ratios below 100 indicate a larger female population. This measure is derived by dividing the total number of males by the total number of females and then multiplying by 100. It is rounded to the nearest tenth.

Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations have sex distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the sex distribution. This is particularly true for areas with a substantial GQ population.
The Census Bureau tested the changes introduced to the 2007 version of the sex question in the 2007 ACS Grid-Sequential Test (http://www.census.gov/acs/www/Downloads/ACS-MP-09_Grid-Sequential_Test_Final_Report.pdf). The results of this testing show that the changes may introduce an inconsistency in the data produced for this question as observed from the years 2006 to 2007

This term appears in connection with several subjects: employment status, journey-to-work questions, class of worker, weeks worked in the past 12 months, and number of workers in family in the past 12 months. Its meaning varies and, therefore, should be determined in each case by referring to the definition of the subject in which it appears. When used in the concepts "workers in family" and "full-time, year-round workers," the term "worker" relates to the meaning of work defined for the "work experience" subject.

Excerpt from:

Social Explorer; U.S. Census Bureau; American Community Survey 2007 Summary File: Technical Documentation.

The data on means of transportation to work were derived from answers to Question 25, which was asked of people who indicated in Question 23 that they worked at some time during the reference week. (See "Reference Week.") Means of transportation to work refers to the principal mode of travel or type of conveyance that the worker usually used to get from home to work during the reference week.
People who used different means of transportation on different days of the week were asked to specify the one they used most often, that is, the greatest number of days. People who used more than one means of transportation to get to work each day were asked to report the one used for the longest distance during the work trip. The category, "Car, truck, or van," includes workers using a car (including company cars but excluding taxicabs), a truck of one-ton capacity or less, or a van. The category, "Public transportation," includes workers who used a bus or trolley bus, streetcar or trolley car, subway or elevated, railroad, or ferryboat, even if each mode is not shown separately in the tabulation. "Carro pÃºblico" is included in the public transportation category in Puerto Rico. The category, "Other means," includes workers who used a mode of travel that is not identified separately within the data distribution. The category, "Other means," may vary from table to table, depending on the amount of detail shown in a particular distribution. The means of transportation data for some areas may show workers using modes of public transportation that are not available in those areas (for example, subway or elevated riders in a metropolitan area where there is no subway or elevated service). This result is largely due to people who worked during the reference week at a location that was different from their usual place of work (such as people away from home on business in an area where subway service was available), and people who used more than one means of transportation each day but whose principal means was unavailable where they lived (for example, residents of nonmetropolitan areas who drove to the fringe of a metropolitan area, and took the commuter railroad most of the distance to work).

Beginning in 2006, the group quarters (GQ) population is included in the ACS. Some types of GQ populations have means of transportation distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the means of transportation to work distribution. This is particularly true for areas with a substantial GQ population.

Beginning in 1999, the American Community Survey questions differ from the 1996-1998 questions only in the format of the skip instructions. Beginning in 2004, the category, "Public transportation" was tabulated to exclude workers who used taxicab as their means of transportation.

Excerpt from:

Social Explorer; U.S. Census Bureau; American Community Survey 2007 Summary File: Technical Documentation.

Places, for the reporting of decennial census data, include census designated places, consolidated cities, and incorporated places. Each place is assigned a five-digit Federal Information Processing Standards (FIPS) code, based on the alphabetical order of the place name within each state. If place names are duplicated within a state and they represent distinctly different areas, a separate code is assigned to each place name alphabetically by primary county in which each place is located, or if both places are in the same county, alphabetically by their legal description (for example, "city" before "village" ).

Census designated places (CDPs) are delineated for each decennial census as the statistical counterparts of incorporated places. CDPs are delineated to provide census data for concentrations of population, housing, and commercial structures that are identifiable by name but are not within an incorporated place. CDP boundaries usually are defined in cooperation with state, local, and tribal officials. These boundaries, which usually coincide with visible features or the boundary of an adjacent incorporated place or other legal entity boundary, have no legal status, nor do these places have officials elected to serve traditional municipal functions. CDP boundaries may change from one decennial census to the next with changes in the settlement pattern; a CDP with the same name as in an earlier census does not necessarily have the same boundary. For Census 2000, for the first time, CDPs did not need to meet a minimum population threshold to qualify for tabulation of census data. For the 1990 census and earlier censuses, the U.S. Census Bureau required CDPs to qualify on the basis of various minimum population size criteria. Beginning with the 1950 census, the U.S. Census Bureau, in cooperation with state and local governments (and American Indian tribal officials starting with the 1990 census), identified and delineated boundaries and names for CDPs. In the data products issued in conjunction with Census 2000, the name of each such place is followed by "CDP," as was the case for the 1990 and 1980 censuses. In the data products issued in conjunction with the 1950, 1960, and 1970 censuses, these places were identified by "(U)," meaning "unincorporated place."

Hawaii is the only state that has no incorporated places recognized by the U.S. Census Bureau. All places shown in the data products for Hawaii are CDPs. By agreement with the state of Hawaii, the U.S. Census Bureau does not show data separately for the city of Honolulu, which is coextensive with Honolulu County.

All places in the Northern Mariana Islands and Guam are CDPs. The Virgin Islands of the United States has both CDPs and incorporated places. There are no CDPs in American Samoa; the U.S. Census Bureau treats the traditional villages as statistically equivalent to incorporated places.

A consolidated government is a unit of local government for which the functions of an incorporated place and its county or minor civil division (MCD) have merged. The legal aspects of this action may result in both the primary incorporated place and the county or MCD continuing to exist as legal entities, even though the county or MCD performs few or no governmental functions and has few or no elected officials. Where this occurs, and where one or more other incorporated places in the county or MCD continue to function as separate governments, even though they have been included in the consolidated government, the primary incorporated place is referred to as a consolidated city.
The presentation of data for consolidated cities varies depending on the geographic presentation. In some hierarchical presentations, consolidated cities are not shown. These presentations include the places within the consolidated city and the "consolidated city (balance)." Although hierarchical presentations do not show the consolidated city, the data for it are the same as the county or county subdivision with which it is coextensive. Other hierarchical presentations do show the consolidated city, county or county subdivision, and (balance) as separate entities. For inventory geographic presentations, the consolidated city appears alphabetically sequenced within the listing of places; in 1990, consolidated places appeared at the end of the listing. The data for the consolidated city include the data for all places that are part of and within the consolidated city. The "consolidated city (balance)" entry shows the data for the portion of the consolidated government minus the separately incorporated places within the consolidated city, and is shown in alphabetical sequence with other places that comprise the consolidated city. For data presentation purposes these "balance" entities are treated as statistically equivalent to a place; they have no legal basis or functions.

In summary presentations by size of place, the consolidated city is not included. The places within consolidated cities are categorized by their size, as is the "consolidated city (balance)." A few incorporated places are partially inside and partially outside a consolidated city. Data tabulations by place will include all territory within the place, while the tabulation for the place within a consolidated city is only for part of the place.

Each consolidated city is assigned a five-digit Federal Information Processing Standards (FIPS) code that is unique within state. The places within consolidated cities and the "consolidated city (balance)" also are assigned five-digit FIPS place codes that are unique within state. The code assigned to each place within a consolidated city is the same as its regular place code; a place that is partially included in a consolidated city does not have a different code for the portions inside and outside the consolidated city. FIPS codes are assigned based on alphabetical sequence within each state.

Incorporated places recognized in decennial census data products are those reported to the U.S. Census Bureau as legally in existence on January 1, 2000, under the laws of their respective states, as cities, boroughs, city and boroughs, municipalities, towns, and villages, with the following exceptions: the towns in the New England states, New York, and Wisconsin, and the boroughs in New York are recognized as minor civil divisions for decennial census purposes; the boroughs, city and boroughs (as in Juneau City and Borough), and municipality (Anchorage) in Alaska are county equivalents for decennial census statistical presentation purposes. In four states (Maryland, Missouri, Nevada, and Virginia), there are one or more incorporated places known as "independent cities" that are primary divisions of a state and legally not part of any county. For data presentation purposes, the U.S. Census Bureau may treat an independent city as a county equivalent, county subdivision, and place.

The U.S. Census Bureau treats the villages in American Samoa as incorporated places because they have their own officials, who have specific legal powers as authorized in the American Samoa Code. The village boundaries are traditional rather than being specific, legally defined locations. There are no incorporated places in Guam and the Northern Mariana Islands. The U.S. Census Bureau treats the three towns in the Virgin Islands of the United States as incorporated places. There are a few incorporated places that do not have a legal description. An incorporated place is established to provide governmental functions for a concentration of people as opposed to a minor civil division, which generally is created to provide services or administer an area without regard, necessarily, to population.